This research plan is directed towards improving artificial kidney technology, one of the specific areas of interest to the National Institute of Arthritis, Diabetes and Digestive and Kidney Diseases. By the middle of 1977 more than 36,000 patients were being regularly treated for uremia by hemodialysis at an annual cost of $650,000,000. Generally, this treatment required the use of large complicated machines at treatment centers. Sorbent regeneration of dialysate is one approach to substantially reducing the cost of this treatment. In addition, such regeneration lends itself better to the production of a more compact dialyser. In fact, an enzyme-based, sorbent system has been developed commercially (i.e., the REDY system). This system, however, still has significant problems related to the NH4+ produced during the enzymatic hydrolysis of urea. The long term objective of this program is to develop an electrochemical urea oxidation reactor that would be part of a safe, compact and inexpensive system for regeneration of hemodialysate. We envision two alternative approaches to the urea reactor as described below. In either case, however, the reactor would be part of a system composed of charcoal for adsorbing all other nitrogenous waste products and ion exchange resins for reducing the levels of phosphate and K+. In one version of the reactor, urea would be oxidized directly at a catalytic metal electrode in the reactor to produce mostly non-toxic oxygen, nitrogen and water which can then be disposed of readily. In the other version, chloride would be oxidized at the reactor anode to produce hypochlorite which would then completely oxidize the urea. Any unreacted hypochlorite ion would be removed by reduction at the reactor cathode or, if necessary, by adsorption on a charcoal bed. Phase 1 of the program would be devoted largely to selecting the reactor configuration that exhibited the best overall performance. In Phase 2, extensive toxicology tests of treated dialysate would be performed. Reactor design would be optimized and scale-up of the reactor to the proper capacity would be carried out. This would be followed by the construction of a full-size prototype regeneration system. This system would first be tested at the laboratory bench, then with animals and finally it would undergo clinical trials with humans at a kidney treatment center.